Walt Rostow, who has died aged 86, had a distinguished career as an economic historian, crowned by the publication in 1960 of The Stages of Economic Growth, a bold attempt, later much contested by specialists, to put forward a conceptual framework for economic development in the context of democratic capitalism. The next year he went to work for President John Kennedy in the White House, and in 1966 he became President Lyndon Johnson's special assistant for national security affairs. In that job he was a passionate advocate of maintaining and increasing the US commitment in Vietnam.

After the Nixon victory in the 1968 presidential election, Rostow suffered for his beliefs. Neither Yale, where he did his undergraduate and doctoral studies, nor the Massachusetts Institute of Technology, where he taught economic history and international affairs for 11 years before going to work in the White House, could find a job for him; and, if rumour is to be believed, several other famous universities, either shocked by his policies or afraid others might be, also refused him. Instead, he went to the University of Texas at Austin, where he and his wife Elspeth, also a distinguished academic, were popular and happy.

Rostow's parents, Jewish immigrants to New York from Russia, were avid socialists. They named him after America's leading poet, Walt Whitman, and his brother, Eugene Victor Debs Rostow, (Obituary, November 28 2002) after America's leading socialist. Walt Rostow, however, was a lifelong anti-communist. He was one of the most brilliant of that group of second-generation immigrants, many of them Jewish, who poured out of America's great private universities in the late 1930s, ready to serve as junior officers in the second world war.

Like so many of them, he was liberal in politics, fiercely ambitious in a polite, controlled style, and socially conservative. Bespectacled, civilised and a charming companion at the dinner table or on the tennis court, he was also as gung-ho as any marine, fiercely anti-communist and a believer in discipline, hard work and the American ideology.

He attended public schools in New York City, and then Yale university, at that time a bastion of the Anglo-Saxon elite. After three years as a Rhodes scholar (1936-38) at Balliol College, Oxford, where he was a contemporary of Edward Heath, Dennis Healey and Roy Jenkins, he went back to Yale to do a PhD, and taught economics at Columbia.

He volunteered for the army and served in Europe as a major in the glamorous intelligence unit, the Office of Strategic Services (OSS), widely derided as standing for "oh-so-social". After the war he joined the state department in Washington as assistant chief of the German-Austrian division, and later worked for the Marshall Plan in Europe. Then came a year teaching history at Oxford and later at Cambridge, and in 1950 he returned to Boston to teach at the Massachussets Institute of Technology.

At MIT, he was also active at its centre for international affairs, one of the places where Cold War doctrine, nuclear theory and "regional studies" were being forged in those years. He was also writing his best-known work, The Stages of Economic Growth. Not by chance, it was sub-titled, An Anti-Communist Manifesto.

In it, Rostow tried to find a common pattern in the history of the economic growth of different societies, from the traditional society, such as medieval Europe or ancient China, where a high proportion of the population was engaged in agriculture and trade exchanges were largely local to an age of high mass consumption, in which society generates a sustainable surplus to improve living standards. The latter part of the book was devoted to exploding Marxist theories of economic development.

The Stages of Economic Growth came under attack from economists and historians. Written from a very Anglocentric point of view, it traced the beginning of modern economic life back to late 18th-century Britain and to the United States. Its historicism is now unfashionable, and today it is despised or dismissed by left and right alike: by the left because it appears to identify economic development with uncritical adoption of American models, and by the right because of its stress on the role of government. Rostow conceded so many non-typical cases, it was said, that it is hard to identify a case that exemplified his theory.

It did, however, fit very comfortably into the mood of the Kennedy administration and its cold war liberals, and it was a huge success, both among students and policy-makers. This was the age of the liberal consensus where there was a broad acceptance of a conservative, anti-communist foreign policy, and a welfare state strategy in domestic politics. A particular merit of Rostow's book, from the standpoint of Washington's policymakers in the Kennedy and Johnson years, was that it was concerned with the third world, though Rostow's experience of developing countries was severely limited.

Rostow was already becoming well known during the Eisenhower years, alongside such other thinkers as Henry Kissinger, William Kaufman and Herman Kahn. In 1958, for example, Rostow was invited to Washington to work with Eisenhower's speechwriter, CD Jackson, on an important presidential message about the Middle East. While he was working on the Eisenhower speech, John Kennedy, then a young senator, invited Rostow out to his house in Georgetown for breakfast. Driving Rostow back to his temporary office in the state department, Kennedy surprised him both by justifying his decision to run for president at such a young age, and by praising Lyndon Johnson as the one man with a better claim on the White House.

When Kennedy became president in 1961, Rostow served for almost a year as deputy to his national security assistant, McGeorge Bundy, another Yale man who had been a wartime major, and wrote a number of speeches for the new president. In December 1961, Rostow was made counsellor to the state department and chairman of its policy planning council, with special responsibility for Mexico, among other areas.

Ten days after Kennedy's murder in 1963, James Reston wrote an article in the New York Times saying that the old Kennedy people were leaving Johnson. President Johnson called Rostow and asked him not to leave. Rostow wrote back, as he later remembered, "basically saying: 'You can count on me'." Indeed, he was invited to help draft Johnson's first state of the union speech. He remembered that Johnson told them to write shorter than they had done for Kennedy. (A Washington joke at the time was that the reason Johnson spoke so slowly was that he was dictating to a stonemason for his words to be set in stone.)

In May 1964, Rostow was asked by two members of Johnson's staff to write down his policy for dealing with Vietnam. He produced a long report, complete with a draft speech for the president. That draft was the one the president used in 1964 when, after the dubious incident of alleged North Vietnamese naval attacks in the Tonkin Gulf, the president announced the escalation of American involvement and US bombing of the north.

Rostow was a man with a deep fund of personal and institutional loyalty. He may have been a New Yorker and an ivy league liberal, but he was also a super-patriot. He was personally devoted to President Kennedy and later even more so to President Johnson, whom he regarded as a great man."The image that some have, of a swashbuckling Southwesterner shooting from the hip," he once said, "is exactly the opposite. He was an extremely careful man, careful about the correct way of doing things."

By the time Rostow took over from Bundy as national security adviser, the Johnson administration was aware that it had a tiger by the tail in Vietnam. Rostow's view remained adamant. The war must be won, and would be won. Negotiations were a waste of time, because Hanoi engaged in them only to encourage American pacifists. At the time, Rostow developed an almost ghoulish enthusiasm for flip-charts detailing the "body count" on which his policies relied, an attitude wildly at variance with his gentler virtues. Ferocity towards theoretical Asian communists contrasted strangely with his kindness to actual human beings. Between 1966, when he went to work as Johnson's national security adviser, and 1969, when he left, the whole climate had changed. Rostow never wavered in his view that the war was right, and that it could have been won. He maintained stoutly that the Johnson administration foresaw the 1968 Tet offensive, and that the offensive was not the disaster it was first perceived as, but, on the contrary, a catastrophe for the National Liberation Front, a view which is more widely held today than it was at the time.

With the peace movement gathering strength, President Johnson withdrew from the 1968 presidential election campaign in order to focus on the war without the distractions of politics. Rostow's position became more and more isolated and he became more and more unpopular, except with a small band of friends. In Cambridge, Massachussetts, as in Washington, supporters of the Vietnam war had become almost pariahs.

The Rostows - at least as their former friends saw it - went to Texas as to an exile on a barbarous shore. But they came to love Austin and to play a very full part in the life of a city that was growing rapidly and a university, where Elspeth Rostow also taught, that was shedding its provincialism. The weather was benign, and allowed Rostow to play tennis for most of the year. The Rostows found themselves in a congenial circle, whose leading lights included Lady Bird Johnson, the president's widow, his nephew Philip Bobbitt, author of The Shield of Achilles, Harry Middleton, director of the LBJ Library, and the African-American law professor and congresswoman, Barbara Jordan.

In 1991 Walt and Elspeth Rostow, together with other community leaders, founded the Austin Project. They were conscious that in an otherwise flourishing city there were large pockets of poverty and unemployment, and in their mid-70s set out to do something about it. The Project has sought to improve the delivery of services of all kinds, including education, to children and young people.

In Austin, Walt Rostow continued to research and to write. In 1998 he wrote The Great Population Spike And After, which he subtitled Reflections On The 21st Century, and in 2002 an intellectual memoir, Concept And Controversy: Sixty Years Of Taking Ideas To Market. In his 80s, he taught undergraduates each autumn, and conducted a graduate seminar each spring. As charming and as pugnacious as ever, he survived what might have been disgrace and was certainly unpopularity as an active, cheerful and still optimistic man.